1. Field of the Invention
The invention relates to a contact reaction tower with internal-circulation ozone for advanced treatment of industrial wastewater.
2. Description of the Related Art
Ozone has the advantages of high reaction speed with organic matters, good reaction effect, no secondary pollution, easily obtained raw materials for production, and convenient use. Thus, it is more and more extensively applied in treatment of industrial wastewater.
The ozone used in water treatment is produced mainly by taking air as raw material. However, the ozone in ozonized air generated by an ozone generator only accounts for 0.6-1.2% (volume). According to the gas state equation and Dalton partial pressure law, the partial pressure of ozone is also 0.6-1.2% of pressure of ozonized air. When water temperature is 25° C., the ozonized air is added in water, and the solubility of ozone is only 3-7 mg/L. Therefore, sufficiently contacting the ozonized air with water, and improving the solubility of ozone as well as the air-water mixing efficiency is the key to enhance the ozonization effect.
The ozonized air for water treatment is in contact with and mixed with water in a special air-water mixing device for the completion of treatment of pollutants, and the contact area, time, ozone concentration, and pressure are decisive factors in mixing efficiency. At present, the ozone-water mixing method mainly includes: (1) an aeration method: this is a traditional, simple, and convenient method, microbubbles formed by ozone with a certain pressure using a microbubble diffuser are in sufficient contact with water, the smaller the bubbles, the greater the depth of water, and the longer the contact time, the better the effect will be; (2) a jet method: the flow speed is increased through the diameter alteration of a device during the flowing process of water in a pipe to form negative pressure suction, the introduced ozone is mixed with water in a pipeline, and the jet method has a high efficiency, however, the installation design and requirements is very strict; (3) a turbine negative suction method: an air passage is additionally arranged through the suction lift of a water pump, negative suction is formed during the water supply to enable the ozone to be introduced to water, the efficiency is high, the air flow control requires particular attention, and the water supply of the water pump will be affected when the air flow is high; (4) a reaction tower method: water is sprayed from a high place to form mist through a high tower, the ozonized air is diffused from a microbubble diffusion device arranged at the bottom of the tower to form rising microbubbles opposite to water flow, the ozonized air is in sufficient contact with water to form ozone water; packings can be involved in this method; the effect is good, but the cost is high, and the packings are easily blocked. In addition, other method for improving the solubility of ozone in water is disclosed in the prior art, for example, developing a machine for making high-concentration ozone water, combining a jet device and a spray nozzle, or using a high-concentration ozone water generation system. However, these methods are not suitable for treatment of industrial wastewater with high flow.